Methane, viii

Davis, A., F. F. Cleveland u. A. G. Meister Substituierte Methane. VIII. Schwingungsspektren, Kraftkonstanten und berechnete thermo-dynamische Eigenschaften fiir Dibrom-Dichlormethan. J. chem. Physics 20, 454 (1952). 

Catalysts. The methanation of CO and C02 is catalyzed by metals of Group VIII, by molybdenum (Group VI), and by silver (Group I). These catalysts were identified by Fischer, Tropsch, and Dilthey (18) who studied the methanation properties of various metals at temperatures up to 800°C. They found that methanation activity varied with the metal as follows ruthenium > iridium > rhodium > nickel > cobalt > osmium > platinum > iron > molybdenum > palladium > silver. 

At the start of the experiment, the CO concentration in the product gas was very low, < 0.01% (Table VIII). The unusually high value (0.71% ) at 186 hrs stream time is the result of an analytical error. At the end of the experiment, after 2307 hrs stream time, CO in the product gas had increased to 0.93% (dry basis), and total methane produced per pound of catalyst was 32 mscf. 

As noted previously, the shifts for the methane state (No. 25 of Table VIII) are best fitted by and for the ketone state by Oij(BA)... 

The first reported work on the kinetics of hydrogenolysis reactions of simple hydrocarbons appears to be that of Taylor and associates at Princeton (2-4, 14, 15), primarily on the hydrogenolysis of ethane to methane. The studies were conducted on nickel, cobalt, and iron catalysts. More recently, extensive studies on ethane hydrogenolysis kinetics have been conducted on all the group VIII metals and on certain other metals as well (16,28-83). 

The successive demethylation scheme of hydrogenolysis just discussed for iron, cobalt, and nickel clearly does not apply to the noble metals of group VIII. This can be seen by examining the product distribution data in Table IV. The amounts of methane observed are much lower than would be expected if the hydrogenolysis occurred by successive demethylation steps. Thus, we have another indication that the noble and nonnoble metals of group VIII behave as two separate classes with regard to their catalytic properties in the hydrogenolysis of hydrocarbons. 

D-glucuronic acid in, VIII, 251-275 Methane, nitro-, syntheses with, VI, 291-318 Methyl ethers. See Ethers, methyl. Molasses, cane, III, 113-128... 

Two extremes emerge from comparison of the Group VIII metals Ni, Rh, Co, and Ru (the left corner of the Group VIII metal block of the periodic table) prefer terminal splitting, already show multiple splitting at rather low temperatures, are the best catalysts (with Os) in hydrogenolysis of ethane (only 2C complexes possible), and catalyze well the reaction of carbon atoms to methane. Pt is the other extreme in all of these respects, with Pd and Ir... 

Throughout these studies, no product other than propane was observed. However, subsequent studies by Sinfelt et al. [249—251] using silica-supported Group VIII metals (Co, Ni, Cu, Ru, Os, Rh, Ir, Pd and Pt) have shown that, in addition to hydrogenation, hydrocracking to ethane and methane occurs with cobalt, nickel, ruthenium and osmium, but not with the other metals studied. From the metal surface areas determined by hydrogen and carbon monoxide chemisorption, the specific activities of... 

Arrhenius parameters for the methanation reaction on alumina-supported Group VIII metals (227b) were close to the line for cracking reactions on several metals (Table III, A). Activity was based on the numbers of surface metal atoms and a compensation relation was described from these data we calculate c = 0.1185 0.0117, B = 15.216 1.068, and oL = 0.491. 

Miscellaneous class reactions. (Section 9.3.) Determine the effect of the following class reagents upon small portions of the original mixture (i) bromine in dichloro-methane solution (ii) potassium permanganate solution (iii) alcoholic silver nitrate solution (iv) 2,4-dinitrophenylhydrazine reagent (v) SchifFs reagent (vi) acetyl chloride (vii) benzoyl chloride (in the presence of aqueous sodium hydroxide) (viii) sodium (only if water is absent) (ix) iron(m) chloride solution and (x) bromine water. 

These activities were based on activities per unit metallic area rather than on activities per gram, as in the results of Fischer and Tropsch. Rostrup-Nielsen suggests that the low activity of the cobalt may be due to the fact that the reaction was carried out under conditions when the cobalt can be oxidized by the steam of the reaction mixture. For the methanation reaction, Fischer, Tropsch, and Dilthey49 give the following order of activities for the Group VIII metals ... 

The Use of Other Metals for Methanation and Steam Reforming. - The review by Vannice133 gives a good description of work in the reactions of CO with hydrogen over metals such as Fe, Ru, Co, and other Group VIII metals. Hence, only a few selected references will be discussed here. 

As seen from Table VIII, in the gas phase the methanation reaction CO + 3H2 —> CH4 + H20, with AN = -49 kcal/mol, is much more exothermic than is the methanol formation CO + 2H2 - CH3OH, with AN = -22 kcal/mol. Thus, the only chance to selectively produce methanol is to have a catalyst on which hydrogenation of H CO species (x =... 

Steam reforming of most hydrocarbons and of course methane occurs only over appropriate catalysts. Catalysts for steam reforming are usually group VIII metals (Carette et al., 2001) whereby Ni seems to be the most effective of this group. Depending on the catalyst s selectivity and on the saturation of the used hydrocarbons, the decomposition of the hydrocarbon may be favoured over the... 

In fact, with the expected trend toward upgrading coal and the depletion of United States natural gas reserves, methanation should further increase in importance. The methanation reaction is thermodynamically favorable even at high temperatures and pressures and there are a variety of metals which catalyze this reaction. Vannice (231) compared the turnover numbers for a variety of Al203-supported group VIII metals and showed that the rate of... 

All the binary Cu/ZnO catalysts were found highly selective toward methanol without DME, methane, or higher alcohols and hydrocarbons detected in the product by sensitive gas chromatographic methods (59). Several of the composites were also found to be very active when subjected to a standard test with synthesis gas C0/C02/H2 = 24/6/70 at gas hourly space velocity of 5000 hr- pressure 75 atm, and temperature 250°C. The activities, expressed as carbon conversions and yields, are summarized in Table VIII. The end members of the series, pure copper and pure zinc oxide, were inactive under these testing conditions, and maximum activity was obtained for the composition Cu/ZnO = 30/70. The yields per unit weight, per unit area of the catalyst or the individual components, turnover rates per site titratable by irreversible oxygen and by irreversible carbon monoxide, are graphically... 

Natrium-Salz VIII, 49 Methan Dimethoxy-phenyl- VII/1,... 

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